The present invention relates generally to mechanisms and tools for the installation of fasteners such as blind bolt fasteners or rivets. More particularly, the present invention relates to mechanisms for automatic installation of the fasteners.
Blind bolt fasteners are commonly used for fastening sheet metal and other structures together. The fasteners typically includes a nut in which a screw is mounted. Installation of the fastener is accomplished by inserting the fastener into a common opening in the structure(s) to be fastened and turning the screw relative to the nut to deform the fastener in a manner to fasten the structures together.
In general, the fastener must have two wrenching surfaces which are engaged by the installation tooling. These wrenching surfaces typically include two flat portions on the end of the screw and a Phillips-type recess in the head of the nut (see FIG. 1A). To install this type of fastener, a non-rotating nose-piece is inserted into the Phillips-type recess in the head of the nut and a rotating driver or wrench adaptor located inside of the nose-piece engages the flats on the screw. The screw is then rotated relative the nut-head to install the fastener.
With hand-held tooling, the proper alignment of the nose-piece and wrench adaptor on the fastener presents no problem. The person installing the fastener inserts it in the hole in the sheet metal or other structure and then carefully adjusts the position of the nose-piece and wrench adaptor so that both wrenching surfaces are securely engaged. The air motor or other drive mechanism is then turned on to install the fastener.
In many situations, automatic installation of fasteners is desirable. Automatic installation of the fasteners presents problems which are not encountered when the fasteners are manually installed. More particularly, during automatic installation of fasteners, the fastener is automatically placed in a pre-drilled hole in the sheet metal or other surface to be fastened. The wrench adaptor inside the nose-piece must be rotating when the wrenching tool is connected to the fastener in order to align its internal drive recess with the flats on the screw. When the wrench adaptor does engage the screw, it causes the fastener to rotate in the hole before the nose-piece engages the recess in the head of the nut. As the nose-piece moves into engagement with the spinning nut, the Phillips-type recess can be distorted and damaged. Many times, the nose-piece will strip or machine the Phillips-type recess to such an extent that the damaged fastener cannot be installed. When this happens, the automatic equipment must be shut down and the damaged fastener removed by hand.
It would be desirable to provide a wrenching tool which can be used for automatic installation of fasteners which automatically and positively engage both the wrench adaptor and nose-piece with the fastener to drive the fastener into place without damaging the recess in the nut head.